SERVER-20498 Send config server optime to shards automatically on all commands via the OP_COMMAND metadata

1 files changed, 38 insertions, 12 deletions

diff --git a/src/mongo/s/client/sharding_connection_hook.cpp b/src/mongo/s/client/sharding_connection_hook.cpp
index 7a178055353..24cd459db27 100644
--- a/src/mongo/s/client/sharding_connection_hook.cpp
+++ b/src/mongo/s/client/sharding_connection_hook.cpp
@@ -42,7 +42,7 @@
 #include "mongo/db/client.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/rpc/metadata/audit_metadata.h"
-#include "mongo/rpc/metadata/config_server_response_metadata.h"
+#include "mongo/rpc/metadata/config_server_metadata.h"
 #include "mongo/s/client/scc_fast_query_handler.h"
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/cluster_last_error_info.h"
@@ -55,6 +55,12 @@ namespace mongo {
 using std::string;
 
 namespace {
+
+// A hook that parses the reply metadata from every response to a command sent from a DBClient
+// created by mongos or a sharding aware mongod and being used for sharded operations.
+// Used by mongos to capture the GLE stats so that we can target the correct node when subsequent
+// getLastError calls are made, as well as by both mongod and mongos to update the stored config
+// server optime.
 Status _shardingReplyMetadataReader(const BSONObj& metadataObj, StringData hostString) {
     saveGLEStats(metadataObj, hostString);
 
@@ -64,7 +70,7 @@ Status _shardingReplyMetadataReader(const BSONObj& metadataObj, StringData hostS
     }
     // If this host is a known shard of ours, look for a config server optime in the response
     // metadata to use to update our notion of the current config server optime.
-    auto responseStatus = rpc::ConfigServerResponseMetadata::readFromMetadata(metadataObj);
+    auto responseStatus = rpc::ConfigServerMetadata::readFromMetadata(metadataObj);
     if (!responseStatus.isOK()) {
         return responseStatus.getStatus();
     }
@@ -74,6 +80,32 @@ Status _shardingReplyMetadataReader(const BSONObj& metadataObj, StringData hostS
     }
     return Status::OK();
 }
+
+// A hook that will append impersonated users to the metadata of every runCommand run by a DBClient
+// created by mongos or a sharding aware mongod.  mongos uses this information to send information
+// to mongod so that the mongod can produce auditing records attributed to the proper authenticated
+// user(s).
+// Additionally, if the connection is sharding-aware, also appends the stored config server optime.
+Status _shardingRequestMetadataWriter(bool shardedConn,
+                                      BSONObjBuilder* metadataBob,
+                                      StringData hostStringData) {
+    audit::writeImpersonatedUsersToMetadata(metadataBob);
+    if (!shardedConn) {
+        return Status::OK();
+    }
+
+    // Add config server optime to metadata sent to shards.
+    std::string hostString = hostStringData.toString();
+    auto shard = grid.shardRegistry()->getShardNoReload(hostString);
+    invariant(shard);
+    if (shard->isConfig()) {
+        return Status::OK();
+    }
+    rpc::ConfigServerMetadata(grid.shardRegistry()->getConfigOpTime()).writeToMetadata(metadataBob);
+
+    return Status::OK();
+}
+
 }  // namespace
 
 ShardingConnectionHook::ShardingConnectionHook(bool shardedConnections)
@@ -93,19 +125,13 @@ void ShardingConnectionHook::onCreate(DBClientBase* conn) {
     }
 
     if (_shardedConnections) {
-        // For every DBClient created by mongos, add a hook that will capture the response from
-        // commands we pass along from the client, so that we can target the correct node when
-        // subsequent getLastError calls are made by mongos.
         conn->setReplyMetadataReader(_shardingReplyMetadataReader);
     }
 
-    // For every DBClient created by mongos, add a hook that will append impersonated users
-    // to the end of every runCommand.  mongod uses this information to produce auditing
-    // records attributed to the proper authenticated user(s).
-    conn->setRequestMetadataWriter([](BSONObjBuilder* metadataBob, StringData) -> Status {
-        audit::writeImpersonatedUsersToMetadata(metadataBob);
-        return Status::OK();
-    });
+    conn->setRequestMetadataWriter(
+        [this](BSONObjBuilder* metadataBob, StringData hostStringData) -> Status {
+            return _shardingRequestMetadataWriter(_shardedConnections, metadataBob, hostStringData);
+        });
 
     // For every SCC created, add a hook that will allow fastest-config-first config reads if
     // the appropriate server options are set.